Answers : (1)

Acetylene and other terminal alkynes (1- alkynes) are weakly acidic in character

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Ex. CH ≡ CH + NaNH2 ————→ H – C ≡ C Na+ + 1/2 H2

(Monosodium acetylide)

The acetylenic hydrogen of alkynes can be replaced by copper (I) and silver (I) ions. They react with ammonical solutions of cuprous chloride and silver nitrate to form the corresponding copper and silver alkynides.

This reaction can be used to distinguish between 2-alkynes and 1-alkynes. 1-alkynes will give this test while 2-alkynes, will not give this test.

CH3 – C ≡ CH + 2[Ag(NH3)2] NO3 ———→ CH3 – C ≡ C – Ag

1-propyne

CH3 – C ≡ C – CH3 + 2[Ag(NH3)2]NO3 ————→ No reaction

EXPLANATION FOR THE ACIDIC CHARACTER

It explained by sp hybridization. We know that an electron in s–orbital is more tightly held than in a p-orbital. In sp hybridization s-character is more (50%) as compared to sp2 (33%) or sp3 (25%), due to large s-character the carbon atom is quite electronegative.